Special care is required for the very first sanding step. Here we need to find the right initial grit size. Normally, 80 is a good start.
But if we suspect that the surface is not flat enough, we may have to start with a coarser grit
Conversely, if the surface is already quite good, we should start right away with a finer grit.
The result of the basic sanding step is a surface level which is good enough for the following finer steps. For this reason, it is best to use a particularly fine hatch for the pencil trick during basic grinding.